A hospital stay could prove harmful to your health - or even fatal. Some 48,000 patients die annually from pneumonia or blood poisoning picked up in the hospital, according to a study that was reported by Reuters.

And hospital-acquired illnesses translated into 2.3 million extra patient days in hospitals, at a cost of $8.1 billion in 2006, according to the study from the Center for Disease Dynamics, Economics and Policy at Resources for the Future, a Washington, D.C.-based think tank.

The research study is one of the first to detail the ever-worsening problem of hospital-acquired illness. It notes that hospital-acquired infections are adding to the spiraling cost of health care in the United States.

"In many cases, these conditions could have been avoided with better infection control in hospitals," said Ramanan Laxminarayan of Resources for the Future, which sponsored the study.

The blood infection sepsis killed one-fifth of the patients who contracted it following surgery, Laxminarayan and his colleagues wrote in the Archives of Internal Medicine. The researchers looked at hospital discharge records from 69 million patients who stayed at U.S. hospitals between 1998 and 2006, and found that the patients who got sepsis after surgery stayed on average 11 days longer, at a cost of about $32,900 per patient. Patients who caught pneumonia in the hospital stayed an additional two weeks at a cost of $46,400. More than 11 percent of the pneumonia patients died, according to the researchers.

"That's the tragedy of such cases," the University of Chicago's Anup Malani, who worked on the study, told Reuters. "In some cases, relatively healthy people check into the hospital for routine surgery. They develop sepsis because of a lapse in infection control and they can die."

Some 1.7 million healthcare-associated infections are diagnosed each year, researchers said.

Handwashing, improved hygiene, and screening patients as they check in are effective measures to prevent infection, but are hard to enforce, studies have shown.